Description, Causes and Risk Factors:
The lumbosacral plexus forms from the ventral rami of the L1-S2 nerve roots and is anatomically divided into lumbar and sacral portions. The lumbar plexus forms within the iliacus muscle lateral to the L1-L4 vertebrae and then courses posterolaterally, just anterior to the iliac wing.
The lumbar plexus consists of anterior and posterior divisions. The anterior division gives rise to the iliohypogastric, ilioinguinal, and genitofemoral nerves (L1-L2), which carry sensory fibers from the skin of the lower abdomen, upper thigh, and lateral genitalia, and the obturator nerve (L2-L4), which provides motor supply to the adductors and gracilis muscles. The posterior division of the lumbar plexus divides into the iliohypogastric and lateral femoral cutaneous nerves (L2-L3), which provide sensation to the lateral hip and thigh, and to the femoral nerve (L2-L3), which carries motor fibers to the psoas, iliacus, sartorius, and quadriceps muscles and provides sensory fibers to the skin of the anterior thigh and medial upper leg.
The sacral plexus arises from the ventral rami of S1-S4 and runs lateral to the border of the sacrum, penetrating the sciatic notch. A portion of the lower lumbar plexus (L4-L5) connects to the sacral plexus via the lumbosacral trunk, which runs over the sacral ala to join the upper sacral plexus within the true pelvis. The anterior division of the sacral plexus provides motor supply to the gemelli, quadratus femoris, obturator internus, and hamstrings; the remaining components continue as the tibial nerve (L4-S3), which provides motor supply to the foot plantar flexors and intrinsic muscles and sensation to the heel and sole. The posterior division continues as the common peroneal nerve (L4-S2) to the peroneal muscles, the tibialis anterior, extensor digitorum, and extensor hallucis muscles and carries sensory fingers from the lateral leg and dorsal foot and toes. The posterior division also gives rise to the superior (L4-S1) and inferior (L5-S2) gluteal nerves, which supply the gluteus muscles. The sciatic nerve, which contains components of the common peroneal and tibial nerves, is part of the posterior division; the posterior femoral cutaneous nerve (S1-S3), which follows the course of the sciatic nerve as a separate bundle, carries sensory fibers from skin of the posterior thigh from the buttock to the knee. The pudendal nerve (S2-S4), along with many smaller nerve bundles, supplies the pelvic floor and genital musculature, as well as the external anal and urethral sphincters. This nerve also carries afferent sensory fibers from the perineum.
The most commonly reported tumors producing lumbosacral plexopathy include carcinomas of the colon and rectosigmoid, gynecologic malignancies, retroperitoneal sarcomas, and lymphomas. Plexopathy is part of the original tumor presentation in approximately 15% of patients. In general, bulky tumors within the pelvis compress and invade the plexus directly. On occasion, tumor tracks along the connective tissue and epineurium of the nerve trunks. This tendency to infiltrate along the nerve may explain why some patients with findings of diffuse plexopathy do not have radiographically demonstrable mass lesions and why in some circumstances the location of the pelvic tumor seems unrelated to the principal site of neurologic involvement.
Significant morbidity from lumbosacral plexopathy occurs due to associated pain, weakness, and sensory deficits. One study noted median survival of 5.5 months after diagnosis. In patients with prostate cancer, symptoms may persist for years and survival may be longer.
Tumors invading the lumbosacral plexus typicallyproduce clinical syndromes based on their level ofinvolvement. Clinical patterns of plexus involvementinclude the upper plexus (L1-L4), the lumbosacraltrunk (L4-L5), and the lower plexus (S1-S4). Plexopathy is usually unilateral, although bilateral findings are present in 25% of patients. Patients typicallypresent with leg pain, which is often followed weeksto months later by progressive leg numbness andweakness. The pain is typically severe, constant, dull,and aching and may have sharp or cramping superimposed local, referred, or radicular components.Pain is often worse when the patient becomes supine;usually the patient has difficulty finding a comfortableposition. Additional pain that worsens with movementor weight bearing generally implies nearby bony invasion. Involvement of the iliopsoas muscle may forcethe patient to assume a position in bed with the hipsand knees flexed, similar to that seen with meningealinflammation. The pain may worsen following a bowelmovement or be exacerbated by a rigorous neuro logic examination. Pain is so common (98%) that itsabsence should raise a red flag regarding this diagnosis.
Symptomatic weakness and sensory complaintseventually develop in 60% of patients. In a series of85 cancer patients with lumbosacral plexopathy andradiographic or surgical evidence of tumor in the region of the plexus objective legweakness was identified in 86%, sensory loss in 73%,focal reflex loss in 64%, and ipsilateral leg edema in47% of patients. Patients typically had tenderness overthe sciatic notch, and straight leg raising tests oftenreproduced their pain. Clinical dysfunction of thelower plexus is most common and is most commonlyseen with colorectal tumors. A dysesthetic syndrome(“hot dry foot”) has been described in as many asone-third of patients due tosympathetic plexus involvement within the pelvis. Incontinence and impotence are typically absent unlessbilateral plexopathy is present.
CT scanning of the abdomen and pelvis is probably the most valuable in diagnosis and gives more information on bony structures. Tumor, bony erosion, and lymphadenopathy are seen in 78% of cases. Clinical findings and CT scan levels do not always demonstrate positive correlation.
Positron emission tomography (PET) scanning can aid in the detection of active malignancy in the plexus region.However, the sensitivity or specificity of PET scanning in the diagnosis of tumor plexopathy is not yet clear.
Bone scanning reveals pelvic, sacral, or vertebral uptake in 60% of patients with lumbosacral plexopathy.
Myelography can be abnormal with malignant plexopathy (in 28-45% of cases).
Routine spinal and pelvic roentgenograms reveal bone destruction in 50% of patients with lumbosacral plexopathy.
Other lab studies depend on the type of cancer and the extent of involvement. Erythrocyte sedimentation rate (ESR), complete blood cell (CBC) count, alkaline phosphatase, protein electrophoresis, prostate specific antigen (PSA), and other cancer-specific labs may be abnormal, depending on the clinical situation. Uremia and hydronephrosis may be an issue with ureter obstruction, especially in patients with gynecologic malignancy.
Cerebrospinal fluid (CSF) studies may reveal elevated protein with negative cytologic findings.
Electromyography [EMG], nerve conduction studies [NCSs]) reveals abnormalities in almost all patients with lumbosacral plexopathy.
The clinical diagnosis of lumbosacral plexopathy is confirmed by magnetic resonance imaging (MRI) or computed tomography (CT) scanning of the affected areas. MRI is preferred, because it is more sensitive and provides better detail than CT scanning.MRI is more accurate in soft tissues. Hydroureter or hydronephrosis are common findings at the time of diagnosis. Diagnosis can be difficult if the scan does not show a mass lesion, but repeating the study in another 4-6 weeks often reveals pathology that was not initially apparent. Increased T2 intensity within nerve trunks, with or without enhancement, has been shown with lumbosacral plexopathy
For physical rehabilitation, the likely progression of neurologic weakness needs to be considered. If the patient is noted to have associated weakness after acute pain has subsided, one may recommend active range of motion (AROM) exercises, with advancement to low resistance exercises. Assistive devices, such as a cane, walker, or wheelchair, may be required for ambulation in patients with weakness of the hip extensors, abductors, or quadriceps, with or without loss of joint position sense. Use of an ankle-foot orthosis (AFO) and, in rare cases, a knee ankle foot orthosis (KAFO) may be beneficial for mobility.
The occupational therapist should assess activities of daily living (ADL) and prescribe appropriate adaptive equipment. In particular, be aware that standing-transfer safety may be impaired in cases in which involvement is more distal than proximal. With more proximal involvement, sit-to-stand transfers also may be affected. Equipment may be used specifically to facilitate dressing and bathing activities involving the lower extremity.
Medical or surgical treatment of the carcinoma when possible is the first treatment of choice. Intra-arterial chemotherapy regionally has limited use in patients with pelvic pain and intractable pain due to plexopathy.
The most commonly used treatment with such plexopathy involves radiation treatment. Subjective improvement has been noted in 85% of patients with regard to symptoms. Objective improvement, including neurologic improvement and reduction in measurable tumor size, has been noted in 48% of patients. However, the average response duration has been found to be only 4 months.
Pain management is an important issue and may require an analgesic ladder approach, including agents specifically for the management of neuropathic pain. Neuropathic pain may respond to nerve stimulation, antidepressants, and antiepileptics. Plexopathy-associated complications, such as contractures, deep venous thrombosis, immobility, and compressive neuropathies, should be anticipated, and early treatment should be provided.
Lymphedema in the lower extremities may be an issue and can be particularly difficult to treat. Treatment should focus on improving the swelling, thus improving pain and function. Initial intervention may include wrapping with nonelastic wrapping, elevation, appropriate retrograde massage techniques, ROM exercises, and education. With improvement in edema, compressive garments should be considered, although these may have to be of a custom type.
Patients with more severe and recalcitrant pain may respond to the use of epidural catheter drug delivery and/or neurostimulatory/neuroablative surgical approaches. Cordotomies have been reported to have good outcomes in Europe. However, pain relief has been noted to be transient. Such ablative procedures carry the risk of sensory and motor deficits. The mortality rate has been significant at 5%.
Occasional relief of chronic pain has been achieved with plexus dissection and neurolysis.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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